Clamping device,especially a mandrel



April 21, 1970' J. TOBLER ETIAL 3,507,591

CLAMPING DEVICE, ESPECIALLY A MANDREL Filed Dec. 5. 1966 6 Sheets-Sheet 1 FIG.1

April 21, 1970 J. TOBLER ETAL 3,50

CLAMPING DEVICE, ESPECIALLY A MANDREL Filed Dec. 5, 1966 6 Sheets-Sheet 2 April 21, 1970 J.TOBLER ETAL CLAMPING DEVICE, ESPECIALLY A MANDREL 6 Sheets-Sheet 3 Filed Dec. 5. 1966 April 21, 1970 J. TOBLER ETAL CLAMPING DEVICE, ESPECIALLY A MANDREL 6 Sheets-Sheet 4 com m GI

April 21, 1970 J. TOBLER ETAL DEVICE, ESPECIALLY A MANDREL CLAMPING Filed Dec. 5. 1966 6 Sheets-Sheet 5 April 21, 1970 J.TOBLER ETAL 3,507,507

CLAMPING DEVICE, ESPECIALLY A MANDREL United States Patent 3,507,507 CLAMPING DEVICE, ESPECIALLY A MANDREL Jakob Tobler, Louvres, and Robert Cochon, Paris, fiance, assignors to Anciens Etablissements T.M.B.-J. Tobler S.A., Louvres, France Filed Dec. 5, 1966, Ser. No. 599,207 Claims priority, application France, Jan. 5, 1966, 44,860; Apr. 21, 1966, 58,568; May 16, 1966, 61,780; Oct. 10, 1966, 79,263

Int. Cl. B23b 31/40 US. Cl. 2792 13 Claims ABSTRACT OF THE DISCLOSURE Clamping device, especially a mandrel, comprising a frame and a hollow diaphragm housed in said frame, said diaphragm being applied against the part to be clamped by the introduction of pressure to the interior of said diaphragm, whose cross-section has a trapezoidal form, the base wall corresponding to the large base of the trapezium being applied against the part to be clamped, while between the walls in the plane of the small base of said trapezoidal section is formed an opening towards a pressure conduit; at least one of the edges of the diaphragm corresponding to one of the apices of the large base of the trapezoidal section of the diaphragm being held fixed laterally in the frame of the clamping device; at least one of the side walls of said diaphragm being inclined towards the interior and arranged in the frame of said clamping device so as to be able to pivot towards the exterior about the edge or edges of said diaphragm, corresponding to the apices of the large base of the trapezoidal section of the diaphragm, under the action of the control pressure; the lateral wall or walls of said diaphragm being guided along the frame in the plane of the surface corresponding to the small base of the trapezoidal section by the wall or walls corresponding to the small base of the trapezoidal section of the diaphragm, and where at least one space is provided between said frame and said diaphragm so as to permit the displacement towards the exterior of at least one of said lateral walls and at least one of said guiding walls.

The present invention relates to a clamping device in which the bottom of a diaphragm is applied against the part or parts to be clamped by means of a pressure-transmission agent.

The invention is essentially directed to devices by means of which the application of the bottom of the diaphragm against the part is regular, uniform, constant in time and with a very high degree of accuracy, ensuring perfect fluidtightness between the part to be -clamped and the bottom of the diaphragm, this object being attained by the particular shape of the diaphragm and the method of its housing in the frame.

The device in accordance with the invention is further characterized by the fact that it may be self-acting, that is to say independent of any source of external pressure.

It is a further characteristic feature of the device according to the invention that any pressure-transmission agent can be utilized for its actuation, such as gases, liquids, liquefied gases or metals in the liquid state, or again synthetic materials in the form of a plastic mass, the use of which avoids the necessity for any fluid-tight joints.

The description which follows below and the accompanying drawings to which this refers will define the device forming the object of the invention and will bring out further characteristic features and advantages.

In the drawings:

FIGS. 1 and 2 illustrate in a diagrammatic manner the principle of the device and of its operation;

FIG. 3 diagrammaticaly illustrates different cross-sections for the device;

FIG. 4 shows by way of example in cross-section, one form of parts which are to be clamped to the exterior;

FIG. 5 shows by way of example a further form of construction of a mandrel for machining between centers and clamping the parts inside their bore;

FIG. 6 shows an alternative form of the mandrel shown in FIG. 2;

FIG. 7 shows a further example of an application for machining in air;

FIG. '8 shows by way of example a cross-section of a form of construction for parts which are to be clamped from the outside;

FIG. 9 shows an example in cross-section of a form of construction of a mandrel for machining between the denters and clamping by means of a tail-stock; and

FIG. 10 shows an example in cross-section of a form of construction for machining between the centers and clamping by means of a key.

The diaphragm M in FIGS. 1 and 2 is housed in a frame 5. In section, this diaphragm is of trapezoidal shape, for

example the shape of an isoceles trapezium, of which the large base forming the bottom 1 is applied against the part 6 or the parts 6 and 6 to be clamped or blocked. The apices O and O of the large base rests against the frame 5. In the position of rest (position I) the lateral sides 2 and 2' of the diaphragm of each form with the base an angle A which are equal in value for the case of an isosceles trapezium. Spaces D and D remain free between the lateral walls 2 and 2 and the frame so that these walls can move laterally under the action of the application pressure p. The small base is provided in its central portion with an opening towards the application pressure conduit. The surfaces 3 and 3' corresponding to the small base constitute guiding surfaces along the frame and further ensure fluid-tightness between the spaces D and D and the interior of the diaphragm M.

In the example shown, the diaphragm M is annular, but it is obvious to those skilled in the art that the diaphragm may be given any desired shape in order to enclose the contours of the part to be clamped.

In the example shown in FIGS. 1 and 2, the two lateral walls 2 and 2' are inclined with respect to the base 1 of the diaphragm M. It will be obvious to those skilled in the art that it would be sufiicient in certain cases for one only of the walls 2 and 2 to be inclined.

The operation of the device in accordance with the invention shown by way of example in FIGS. 1 and 2, is as follows:

The diaphragm and the conduits being filled with a pressure-transmission agent, are subjected to a pressure p generated by any possible means P for example a piston 7 arranged in the frame, actuated by mechanical means which may be a clamping key, a pull-rod, a screw actuated by a key, etc. This method of actuation enables the device to be independent and permits its use for all cases in which the introduction of a pressure-transmission agent is difficult or almost impossible to achieve.

The pressure p acts on the internal surfaces 1, 2, 2', 3 and 3' of the diaphragm M. The central portion of the base is firmly applied against the part 6. However, experience has shown that for many reasons, for example the quality of the materials employed for the diaphragms, or again the method of their housing in the frame, in the case of diaphragms of known shapes and housed in a manner already known, the application of the extremities of the base against the part or the parts to be clamped was effected irregularly, resulting in a clamping behaviour which was not very accurate, irregular, and permitted the infiltration of various materials 3 between the diaphragm and the part or parts to be clamped. In fact, in the known clamping membrane devices, only a part of the base of the diaphragm which has a tendency to become domed under the effect of the pressure, is applied, and the position of the part to be clamped is ill-defined and the clamping is inaccurate.

In the diaphragm of the device according to the invention, the pressure p acting at right angles against the lateral walls may be split-up into two components: a component p parallel to the base 1 and a component p vertical with respect to the base 1. The horizontal components p move the lateral walls 2 and 2' towards the exterior (position II). These walls pivot about and 0, held fixed by the frame and the part to be clamped, through an angle B, and are guided along the frame by the guiding surfaces 3 and 3. This pivotal movement of the lateral walls guided at their upper extremities, causes a tendency to force down the pivots O and O and therefore to grip the part 6 at the points 0 and O.

The pressure p also acts on the surfaces 3 and 3' and applies them firmly against the frame, thus ensuring fluid-tightness between the spaces D and D and the interior of the diaphragm M. Sealing joints 9 and 9' may be provided as shown in FIG. 2. When the pressure is released, each of the parts of the diaphragm returns to its position of rest, either due to the elastic qualities of the material of the diaphragm or by elastic restoring means.

The diaphragms may be made of any desired material having the necessary qualities: steel and metal generally, rubber, etc.

The device further permits of easy interchangeability of the diaphragms with others of different dimensions in order to permit clamping of parts of different diameters.

It may sometimes be advantageous to arrange the guiding surfaces 3 and 3' of the diaphragm M otherwise than with the arrangements shown in FIGS. 1 and 2.

FIG. 3 shows by way of example crosssections of shapes W, X, Y and Z (see also FIGS. 1 and 2).

These shapes may sometimes have an advantage in cases of use of special pressure-transmission agents, such as liquefied gases (low temperatures) or metals in the liquid state (high temperatures), etc.

The invention thus results in a clamping and/or looking device having great precision and exceptional qualities of fluid-tightness and which, in addition, may be independent of any external source of fluid.

Very many applications may be contemplated. For example, brakes acting on a shaft or again parking and safety brakes for vehicles of all kinds; anti-theft devices for automobile vehicles acting on the steering column or combined with the parking brake; couplings between two shafts, and especially precision couplings; couplings and connections for pipes; application devices for brake linings and in general in all the problems of clamping and/or locking, but especially for mandrels of machine tools.

In known types of diaphragm mandrels, the pressure applied on the diaphragm is liable to cause an irregular deformation of this latter, the central portion of the diaphragm having a tendency to become domed towards the part to be clamped. There is thus often obtained an irregular and inaccurate clamping and there is risk of fouling with dirt between the diaphragm and the clamped part, the extremities of the diaphragm being badly applied; the precision of clamping is comparatively low and wear of the diaphragm is rapid.

On the other hand, a mandrel in accordance with the invention has numerous advantages: it permits of regular and uniform application of the diaphragm against the whole application surface of a part to be clamped; it does not permit any infiltration between the part and the diaphragm; it makes it possible to produce a mandrel having a considerable useful life and which is easy to 4 maintain, and to produce a mandrel comprising a diaphragm interchangeable with other diaphragms of different dimensions, for the clamping and successive machining of parts having dimensions which are different from each other.

The mandrel according to the invention shown by way of example in FIG. 4 comprises a cylindrical frame 10, hollow, and housing an annular clamping diaphragm 2a. The clamping pressure is applied in the example shown bymeans of a hydraulic liquid. This liquid is introduced into the conduits and spaces for application of pressure by the filling plug 3a. An air release plug 4a is provided for the filling operation.

The diaphragm 2a of a material of suitable quality, for example of steel, is arranged circularly in the body. In cross-section, its section is a trapezium, the large base of which constitutes the bottom 21. The opposite side shows in its central portion a circular opening 22 towards the pressure conduit 5a. The two lateral extremities 23 and 23' of this side rest against the wall 711 of the frame, fluid-tightness being ensured by the packing joints 6a and 6a.

Each of the lateral extremities 23 and 23 is continued, on the one hand by the lateral walls 25 and 25', and on the other hand by the elements 24 and 24 which are supported against the wall 7a of the frame 1a.

The part 24 of the diaphragm can move freely towards the left (in the drawing) guided on the wall 7a of the frame 1. The part 24 is fixed. The lateral walls 25 and 25 are inclined towards the base at an angle A, chosen in such manner as to obtain the best possible clamping of the part to be machined.

An application piston 10 is arranged at the extremity opposite to that of the clamping side of the mandrel. It is actuated by a pull-rod 11. The piston is provided with a stud 12 in order to prevent its rotation while ermitting its sliding movement in the direction of the arrows f f An intermediate part 13 ensures the communication between the conduits and spaces under pressure.

The liquid thus fills the whole of the spaces and conduits 14, 15, 16, 17, 5 and the interior 27 of the diaphragm 2a.

The liquid coolant used for machining is supplied through the conduit 18 and is evacuated from a chamber 19 through evacuation holes 26 in the frame (shown in broken lines in FIG. 4). This chamber 19 is also open towards the part to be machined and thus permits evacuation of the swarf at the same time.

The operation is as follows:

A part which is to be machined on the faces; 31 and .31 and in the bores 32 and 33, is introduced into the mandrel, the maximum tolerance on the diameter M of the part to be clamped being preferably equal to or less than of the diameter M The pressure is then effected by applying a force on the pull-rod 11 in the direction of the arrow h. This force is a function of the diameter M of the part to be clamped and of its tolerance.

The piston 10 acts on the liquid in the conduits and spaces 17, 16, 14, 15, 5a and 27.

In the internal space of the diaphragm 27, there is then established a pressure acting perpendicularly on each point of the bottom 21, of the extremities 23 and 23' and of the lateral walls 25 and 25'. The pressure p acting on each point of the lateral walls can be split-up into a horizontal component p and a vertical component p The clamping effect at the extremities is accentuated by the action of the horizontal components p In fact, the wall 25 being capable of moving towards the left guided by the element 24- along the Wall 7 of the frame 1a, the bottom 21 of the diaphragm being firmly pressed against the part 30 to be machined and being thus fixed, the wall 25 carries out a pivotal movement about the apex 28 between the wall 25 and the bottom 21. This pivotal movement of the wall results in a clamping effect on the part 30 by the extremity of the bottom 21 at apex 28.

A similar effect can be obtained for the wall 25. The diaphragm is held on this side. However, the wall 25' is not supported and can be freely deformed by the effect of the pressures p which causes the large base to slide to the left. There is thus also obtained an effect of pivotal movement and therefore of clamping at the point of the apex 29.

The lateral extremities 23 and 23 are also subjected to the pressures p and are applied firmly against the wall 7a of the frame 1a together with the joints 6a. The fluidtightness between the diaphragm and the frame is ensured by this means, together with the concentricity of the assembly.

A clamping effect between the mandrel and the face 35 of the part 30 to be clamped is obtained by the pivotal movement of the wall 25 and movement in the axial direction of the parts 23-24 of the diaphragm 2a.

The assembly is effected in such manner as to permit rapid interchangeability of the diaphragm. It is thus possible to change rapidly from the machining of a part 30 having a diameter M to another part having a different diameter, the dimension e of the diaphragm being inversely proportional to the diameter M of the part to be machined.

FIG. 5 shows an example of a mandrel for fixing between centers. The part 300 to be machined is mounted round the annular diaphragm 2b, identical in operation to that shown in the example of FIG. 1, except that the clamping is effected radially towards the exterior, against the surface 301 of the part 300.

The operation is as follows:

The machine center is applied against the center 101 of the piston 100 with a certain force. As the piston can slide in the bore 70 of the frame 1b, the liquid contained in the spaces 27, 50, 170 is put under pressure which acts on the lateral walls 25 and 25', the extremities 24 and 24' and the bottom 21 in a similar manner to that described for the example shown in FIG. 1. When the center is withdrawn, a spring 171 helps to restore the neutral position of rest. A screw 111 isolates the conduits 50 from the center 101 and serves as a drain plug.

FIG. 6 involving diaphragm 2c shows a mandrel between centers for the clamping of parts 300 intended to be clamped inside their bore. In this example, the clamping pressure is created by screwing-up the screw in the direction of the arrow i the lower face 53 of the head 52 of the screw 51 acting as a piston. Sealing joints 54 and 55 between the head 52 and the frame 1c are provided. A screw 111 isolates the opening 101 from the pressure spaces 50 and serves as a drainage plug. The pressure is released by unscrewing the screw 51 in the direction of the arrow f In FIG. 7, there is shown a mandrel according to the invention utilized for the machining in air of a part 300, arranged concentrically on the diaphragm 2d, the mandrel being fixed by a plate to the machine. In this form of embodiment, a piston 100 is guided in the space 171, the clamping force being applied in the direction of the arrow on the part 100 acting as a pull-rod. The pressure acts on the liquid in the spaces and conduits 170, 50 and 27, so as to apply the bottom of the diaphragm 21 against the part 300 to be clamped.

A clamping effect is also obtained between the part 300 and the face 210 by the tractive pull applied in the direction of the arrow i by displacement of the lateral wall 25 of the diaphragm 2d. An element 111 ensures fluid-tightness between the conduits 50, the space 170 and the atmosphere, and also serves as a drainage plug.

The figures which follow show forms of construction of mandrels in which the two lateral walls of the diaphragm can move freely towards the exterior under the applied pressure.

The mandrel in accordance with the invention, shown by way of example in FIG. 8 comprises a casing 1e housing an annular clamping diaphragm 2e. In the example shown, the clamping pressure is applied through the intermediary of a hydraulic liquid.

The diaphragm 2e, preferably of steel, but which may be of any other suitable material has, in cross-section, the form of a trapezium, the large base of which forms the bottom 21. The side opposite to the bottom is provided with an opening 22 towards the pressure conduit 5e. The two side extremities 23 and 23' which act as centering guides, are supported against the wall 7e of the frame 1e. Fluid-tightness is ensured by the packing joints 6e and 6e.

The extremity 23 is turned towards the exterior, a space s separates the edge of the extremity 23 of an element 8 of Which the lower part 8' rests against the apex 28 of the bottom 21 of the diaphragm 2e.

A certain number of these elements 8 can be uniformly spaced apart along a circle in the frame 1e, and are fixed to the frame by screws 8' or alternatively the element 8 may be in a single piece with the recesses and passages for the cooling liquid coming from the conduit 19 and evacuated through the holes 26 with the swarf and dirt.

The extremity 23 of the diaphragm 2e 1s turned towards the interior. An element 8 is provided having its lower portion 8' resting against the apex 29 of the bottom 21 of the diaphragm 22.

The element 8 is formed in such manner as to create a free space D along the side wall 25'.

Thus, both the side wall 25 and the side wall 25 can move towards the exterior under the liquid pressure obtaining in the interior 27 of the diaphragm 2e.

A clamping pressure p introduced by the conduit 5p is applied on the bottom and forces this latter firmly against the part 30 to be clamped.

The side walls 25 and 25' are free to move towards the exterior. i

The apices 28 and 29 of the base 21 of the diaphragm 2e being blocked respectively by the parts 8 and 8 the movement of the side walls 25 and 25' results in a pivotal action about the said apices 28 and 29, the guiding of the elements on the side opposite to the base 21 along the wall 7e of the frame 12 being ensured by the extremities 23 and 23' of the diaphragm 2e. Thus, the extremity 23 can move laterally in the space s and the extremity 23' in the space s.

The horizontal components 12 of the pressure p acting on the side walls causes them to pivot and accentuate the clamping effect at the points of the apices 28 and 29, thus ensuring a strict and accurate clamping of the part 31 in the mandrel, With perfect fluid-tightness between the bottom 21 of the diaphragm and the part 31.

FIG. 9 shows by way of example a mandrel for fixing between centers with clamping by a tail-stock, operating in a manner similar to that shown in the example of FIG. 2.

In the present example, the bottom 21 of the diaphragm 2 is applied against the part 300 mounted round the circular diaphragm. The pressure introduced through the conduit 50 acts in the interior 27 of the diaphragm on the bottom 21 and on the side walls 25 and 25.

The apex 28 of the bottom 21 rests against the frame 10 and the apex 29 against a part 81 held on the mandrel by a ring 8 for example. Spaces D and D are provided on each side of the lateral walls 25 and 25', permitting their movement towards the exterior, their guiding on the frame 1 being effected by the centering parts 23 and 123 of the diaphragm 2f. Fluid-tightness is obtained by means of the packing joints 6] and 6f between the frame 10 and the parts 23 and 23' which, in the example shown, are in the form of a loop turned towards the interior.

FIG. shows a further example of a mandrel for fixing between centers, but with clamping by a key.

In this example, the diaphragm 2g rests at its apices 28 and 29 against a part 810 fixed on the frame 100 by screws 812 on the one hand and on the other hand on a part 811 held by a ring 813.

Spaces s and s permit the movement towards the exterior of the centering guides 23 and 23. The pivotal movement of the lateral walls 25 and 25' is rendered possible by the arrangement of the spaces D and D Packing joints 6g and 6'g ensure fluid-tightness between the frame 100 and the guides 23 and 23 arranged in the shape of a Z towards the exterior. Packing joints 600 and 601 are mounted in the parts 810 and 811 so as to ensure the fluid-tightness of the spaces D and D All the forms of construction described utilize a hydraulic liquid as a pressure-transmission agent, which necessitates the provision of sealing joints between the diaphragm and the frame, between the pressure-application piston and the frame, etc.

The use of a pressure-transmission agent which does not necessitate the provision of such fluid-tight joints would therefore offer a great many advantages.

Certain metals such as mercury in the liquid state could be employed.

The applicants have obtained particularly advantageous results with plastic masses of synthetic material, for example, a mass which is essentially composed of parafiined cellulose and methyl, such as manufactured in Germany by the Dynamit Aktiengesells-chaft, and sold under the trade name of Weichmipolam PVC 5319.

The invention has thus provided a clamping device and in particular a mandrel having exceptional qualities. It will of course be understood that the forms of construction described and shown in the text and the drawings are only examples and that other forms of construction of the device, especially as regards its application, remain within the scope of the invention.

What we claim is:

1. A clamping device comprising a hollow clamping diaphragm having a cross-section with a large base, a small base means parallel to said large base and inclined sides connecting the bases, the small base means being provided with an opening, supporting means for supporting the diaphragm with the large base exposed for engaging a work piece and clamping the same and for relatively free displacement of said sides about pivot points at the intersection of the sides with the said base and base means, said opening dividing the small base means into separate sections, said supporting means further supporting the diaphragm so that at least one of the sections is free to move towards and away from the other of the sections and so that said large base can move relatively towards and away the small base means with an attendant adjustment of the inclination of the sides with respect thereto, and pressure means to inject a pressure medium through said opening into said diaphragm to urge the large base against said workpiece.

2. A device as claimed in claim 1, wherein the sections of the small base means extend towards each other from the respective sides.

3. A device as claimed in claim 1, wherein the sections of the small base means extend away from each other from the respective sides.

4. A device as claimed in claim 1, wherein the sections of the small base means extend inwardly and outwardly of the respective sides.

5. A device as claimed in claim 1, wherein the sections of the small base means extend in the same direction from the respective sides.

6. A device as claimed in claim 1, wherein the diaphragm is an annular member the large base of which is radially outwards of the small base means.

7. A device as claimed in claim 1, wherein the diaphragm is an annular member the large base of which is radially inwards of the small base means.

8. A device as claimed in claim 1 comprising packing elements on the supporting means between the latter and the small base means of the diaphragm.

9. A device as claimed in claim 1 comprising an extension on said other section engaged by the supporting means to hold said other section against displacement.

10. A device as claimed in claimed in claim 1, wherein the pressure means includes a displaceable piston engaged in the said supporting means.

11. A device as claimed in claim 1, wherein the pressure means includes a displaceable member threadedly engaged in the supporting means.

12. A device as claimed in claim 1, wherein the pressure medium is a fluid.

13. A device as claimed in claim 1, wherein the pressure medium is a plastic mass.

References Cited UNITED STATES PATENTS 3,250,542 5/1966 Winnen et a1. 2794 3,130,978 4/ 1964 Roojen 2794 2,534,527 12/1950 Myers 279-4 ROBERT C. RIORDON, Primary Examiner US. Cl. X.R. 

